This invention relates generally to refrigeration systems and in particular to an energy efficient refrigeration apparatus in a refrigerator to handle different cooling demands.
In most conventional refrigerators, a need for cooling in one refrigerator compartment results in the operation of the all components in the refrigeration apparatus and the delivery cooling air to all compartments in the refrigerator. For example, a thermostatic control detecting a temperature above a set point temperature in one compartment generates a signal to start a compressor, beginning the pumping and compressing of the refrigerant, and simultaneously the evaporator fan is energized to produce air flow over the coils of the evaporator in order to cool air that is directed into the refrigerator compartment. The cooled air then commonly passes into a plenum in the refrigerator in which the flow is split such that the majority of the air flow is directed into a freezer compartment and the other portion of the air flow is directed into fresh food compartments of the refrigerator. The split of air flow between the freezer and fresh food compartments is made by a damper that directs the majority of the air flow into the freezer compartment; because the air flow is always split between freezer and fresh food compartments, the refrigeration apparatus always chills the cooling air to a sub-freezing temperature, regardless of which compartment (fresh food or freezer) is in need of cooling. In most conventional refrigerators the position of the damper is either fixed at time of manufacture or adjustable within a small range, either manually by the operator or by an automated control within a limited range of adjustment such that the majority of air flow in all damper settings is still directed to the freezer compartment.
Operation of the refrigerator in this manner results in certain inefficiencies that increase the energy consumption of the refrigerator. Notably, in such arrangements the full capacity of the compressor is always used regardless of the cooling demand that necessitated the start up of the refrigeration apparatus (such as a need for cooling the fresh food but not the freezer compartment).
It is desirable from the standpoint of reducing energy consumption to operate the refrigeration apparatus so as to tune the cooling capacity of the compressor with the cooling demand precipitating the operation of the compressor. For example, use of dual evaporators to meet different cooling demands can improve refrigerator energy efficiency, as is disclosed in U.S. Pat. Nos. 4,910,972; 4,918,942; 5,103,650; and 5,134,859, which are assigned to the assignee of the present invention and which are incorporated herein by reference.
It is thus an object of this invention to provide a refrigeration system that improves the energy efficiency of the refrigerator through selective operation of the compressor at different cooling capacities corresponding to cooling demand in the refrigerator. It is a further object of this invention to provide a dual stage compressor that is readily adapted for use in a dual evaporator refrigeration system.